An electrical part or component (on-vehicle unit) such as a light (illuminant), a warning lamp or an air conditioner of an automobile is manipulated by depressing a corresponding one of the switches installed on a panel of a driver's seat. Conventionally, in order to transmit commands to on-vehicle units through these switches, a lot of signal lines were arranged in a vehicle. In addition, electric power supply lines for supply of electric power used to drive the on-vehicle units were also arranged separately from these signal lines. The wiring is bundled together and is called a wire harness.
In recent years, however, the number of on-vehicle units with which an automobile is loaded has been increased year by year with the advance of the technology concerned with a car navigation system, an on-vehicle audio system or a TV. Thus, the number of signal lines and electric power supply lines used in these on-vehicle units has been increased accordingly. Hence, a diameter of the wire harness into which the signal lines and the electric power supply lines are bundled has also been increased, and a weight of the wire harness has also been increased. As a result, a problem arises in that it becomes difficult to ensure a wiring space, a rate of fuel consumption of an automobile is made worse due to an increase in weight, and so forth.
In addition, there also arises a problem in that a very hard work is required for drawing signal lines for electric equipment from a wire harness into which an enormous number of signal lines and electric power supply lines are bundled and connecting these lines in the vicinities of the electric equipment.